JP2003156646A - Method of depositing optical film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of depositing an optical quality film by plasma enhanced chemical vapor deposition (PECVD) by which a desirable difference in refractive indices between adjacent films is realized. SOLUTION: The method of depositing an optical quality film by PECVD including the following steps is provided. Namely, the method includes two steps, (i) a step in which a space defined by six dimensions is created wherein five dimensions thereof correspond to five respective independent variables of which a set of four independent variables relate to the flow-rate of respective gases a plurality of kinds, a fifth independent variable relates to total pressure, and a sixth dimension relates to observed Fourier transform infrared spectroscopy (FTIR) characteristics, and (ii) a step in which an optical film is deposited while maintaining three of the set of four independent variables substantially constant as well as the fifth independent variable, and varying a fourth of the set of four independent variables to obtain desired characteristics in the sixth dimension.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical film, more specifically, for example, an optical Mux /
Demux device (multiplexer / demultiplexer)
Optical quality silica film in the manufacture of waveguides for optical fiber (dep)
osit) method.

[0002]

2. Description of the Related Art An optical multiplexer (Multipl)
exer) (Mux) and demultiplexer (Dmu)
For optical devices such as x), International Telecommunications Union (ITU) for wavelength division multiplexing (WDM) transport networks, and Fiber-To-The-Home (F).
1.30 bidirectional narrow optical band (bi-d) recommended for optical access networks using TTH technology.
Directional Narrow optical
band) and / or 1.55 μm video signal optical band, very transparent.
nt) Optical quality silica waveguides are required.

Such a waveguide is, for example, a Uchid
a N.A. Passive Array Hybrid WDM Module Integrated with Spot Size Converter Integrated Laser Diode for FTTH, Electronic L
etters, 32 (18), 1996; Inoue.
Y. Silica-based planar lightwave circuit for WDM systems by
IEICE Trans. Electron. , E80
C (5), 1997; Inoue Y. PLC Hybrid Integrated WDM Transceiver Module for Access Networks, by NTT Review, 9 (6),
1997; and Takahashi H .; By WDM
Arrayed-wave grating for system
egide grating) wavelength division multiplexer, NTT
Review, 10 (1), 1998 ;.

These silica waveguides basically consist of three films: a buffer,
Core and claddin
g). For simplification, the buffer and cladding are usually of the same composition and usually have the same characteristics:
It has the same refractive index at 1.55 μm wavelength (or 1.30 μm wavelength). 1.55 μm wavelength (and / or)
Constrain the laser beam of 1.30 μm wavelength (co
To be nfine), the core must have a higher index of refraction at the 1.55 μm wavelength (and / or 1.30 μm wavelength) than the buffer (cladding). 1.55 required between core and buffer (clad)
The refractive index difference at the μm wavelength (and / or 1.30 μm wavelength) is referred to as “delta n” (delta-n). This "delta n" is one of the most important properties of silica waveguides. 1.55 μm wavelength (and / or 1.30 μm)
In the (wavelength) optical domain, it is very difficult to produce optically transparent buffers (claddings) and cores with suitable "delta n".

In order to obtain these high performance optically transparent silica waveguides, various technical techniques have been tried in the prior art. The first method is Flame Hydrolysis Dep.
position) (FHD). This technique involves the fusion of a plurality of glass particles in hydrogen, oxygen and other gases, and then 1200-200.
Some post-deposition annealing at 1350 ° C. is included. The second method is a high pressure stream.
(HPS) technique. This technique involves the direct growth of silica films from silicon at very high temperatures in an oxygen-containing atmosphere, followed by annealing at very high temperatures of about 1000 ° C. The third approach is the electron beam evaporation (EBVD) technique of quartz or silica at about 350 ° C, followed by annealing at a very high temperature of 1200 ° C.

Another approach is plasma enhanced chemical vapor deposition (PE
CVD) technique. Such techniques are described in the following documents: Low temperature plasma chemical vapor deposition of silicon oxynitride thin film waveguides, Applied Opti.
cs, 23 (16), 2744, 1984; Valet.
te S. Novel Integrated Optical Multiplexer-Demultiplexer, ECIO ', Obtained on Silicon Substrate
87, 145, 1987; Grand G. et al. Low Loss PECVD Silica Channel Waveguide for Optical Communication, Ele
ctron. Lett. , 26 (25), 2135, 1
990; Bruno F .; Enhanced Chemical Vapor Deposition of Low-Loss SiON Optical Waveguide at 1.5 μm Wavelength, App
Lied Optics, 30 (31), 4560, 1
991; Kasper K .; Deposition of High Quality Silicon Oxynitride Waveguides by IEEE Tee
rans. Photonics Tech. Let
t. 3 (12), 1096, 1991; Lai Q .;
A simple technique for the manufacture of low loss silica waveguides by
Elec. Lett. , 28 (11), 1000, 19
92; Bulat E .; S. Fabrication of Waveguides Using the Low Temperature Plasma Treatment Technique by J. Vac. Sci. Tec
hnol. All (4), 1268, 1993; Imo
to K. High index difference and low loss optical waveguide manufactured by a low temperature process by Electron. Le
tt. , 29 (12), 1123, 1993; Bazy.
lenko M. V. Temperature PECVD with significantly improved loss in the 1.50-1.55 μm wavelength range according to
Channel Waveguide Manufacturing, IEE Photonics
Tech. Lett. , 7 (7), 774, 1995;
Liu K. Hybrid Optoelectronics Digital Tunable Receiver, SPI by
E, Vol 2402, 104, 1995; Yokoh.
ama S. Optical waveguides on silicon chips by J.
Vac. Sci. Technol. A13 (3), 62
9, 1995; Hoffmann M .; By PECV
Low temperature nitrogen-doped waveguide with small core dimensions on silicon, ECIO, manufactured by D / RIE
'95, 299, 1995; Bazylenko M .;
V. Hollow cathode for integrated optics applications by
ow cathode) pure and fluorine-doped silica films deposited in a reactor; V
ac. Sci. Technol. A14 (2), 33
6, 1996; Durandet A .; By PECV
Silica Buried Channel Waveguides Fabricated at Low Temperature Using D, Electronics Letters, 32
(4), 326, 1996; Poenar D. et al. Materials suitable for thin film silicon by thin films
ilicon-compatible material
l) optical properties, Appl. Opt. 36 (21),
5122, 1997; Agnihotri O .; P. Silicon Oxynitride Waveguides for Optoelectronic Integrated Circuits, Jpn. J. Appl. Phy
s. , 36, 6711, 1997; Boswell.
R. W. Deposition of Silicon Dioxide Films for Integrated Optical Applications Using Helicon Diffusion Reactors, Plasma Treatment of Semiconductors, Klumer Academic
Publishers, 433, 1997; Hoff
mann M.M. Low-loss fiber-matching with small core dimensions for optical communication systems
ched) Low temperature PECVD waveguide, IEEE Photo
onics Tech. Lett. , 9 (9), 123
8, 1997; Pereyra I .; , High quality low temperature DP
ECVD Silicon Dioxide, J. Non-Cryst
alline Solids, 212, 225, 199
7; Kenyon T. , Luminescent studies of silicon-rich silica and rare-earth-doped silicon-rich silica, Fou
rth Int. Symp. Quantum Conf
element Electrochemical S
ociety, 97-11, 304, 1997; Ala.
yo M. Thick SiO _x N _y and SiO ₂ films obtained at low temperature by the PECVD technique by Thin S
old Films, 332, 40, 1998; Bu
lla D.I. TEOS for integrated optical waveguide applications
PECVD Silicon Oxide Film Deposition, Thin Solid Films, 334, 6
0, 1998; Canning J. et al. By Negative index grating in germano silica planar waveguide
ng), Electron. Lett. , 34 (4),
366, 1998; Valette S. et al. In the field of integrated optics technology at LETI to achieve passive optical components by J. of Modern Opti
cs, 35 (6), 933, 1998; Ojha S. et al.
Polarization-ins due to
A) with very low crosstalk
Ele, a simple method for manufacturing a WG grating device
ctron. Lett. , 34 (1), 78, 199
8; Johnson C .; Annealing of Waveguides Formed by Ion Implantation of Silica-on-Si by N.
nstruments and Methods in
Physics Research, B141, 67
0, 1998; Ridder R. et al. Silicon oxynitride planar waveguide structure for optical communication applications, IEEE
J. ofSel. Top. In Quantum El
electron. 4 (6), 930, 1998; Ger.
mann R.M. Silicon oxynitride film for optical waveguide applications ^by, 195 th meeting of
the Electrochemical Soci
ety, 99-1, May 1999, Abstrac
t 137, 1999; Worhoff K .; Enhanced Plasma Enhanced Chemical Vapor Deposition Silicon Oxynitride, Sensors and Act for Integrated Optical Applications
uators, 74, 9, 1999; and Offrei
n B. Tunable optical add-after-drop with flat passband for WDM networks according to US Pat.
drop) filter, IEEE Photonics
Tech. Lett. , 11 (2), 239, 19
99.

A comparison of these various PECVD techniques is summarized in the table below.

[0008]

[Table 1]

This table compares methods that have been attempted to improve the refractive index of the buffer (cladding) and core while attempting to reduce optical absorption. These various techniques can be grouped into the following major categories: That is, PECVD using an unknown chemical in combination with an unknown boron (B) and / or phosphorus (P) chemistry to adjust the refractive index of the silica film; PECVD using TEOS in combination with an unknown means of adjusting; PECVD using oxidation of SiH ₄ by oxygen in combination with an unknown means of adjusting the refractive index of a silica film;
CF ₄ (Si for adjusting the refractive index of the silica film
S with oxygen combined with H ₄ / oxygen / CF ₄ flow ratio)
PECVD using oxidation of iH _4; in combination with _N 2 O to adjust the refractive index of the silica films _(SiH 4 / _{N 2} O flow ratio), PECVD using oxidation of SiH ₄ by the _{N 2} O; silica in combination with _{N 2} O and _N 2 for adjusting the refractive index of the film _{(SiH 4} / N 2 O / _{N 2} flow rate ratio), PEC oxide is used in the SiH ₄ by _{N 2} O
VD: N ₂ O for adjusting the refractive index of the silica film
And Ar (SiH ₄ / N ₂ O / Ar flow rate ratio),
PECVD using the oxidation of SiH ₄ by N ₂ O; and N ₂ O and N for adjusting the refractive index of silica films
H ₃ (SiH ₄ / N ₂ O / NH ₃ flow ratio),
PECVD using oxidation of SiH ₄ by N ₂ O, a category group.

[0010]

In any of these conventional techniques, for example, a high quality film having an ability to create a desired refractive index difference between adjacent films forming a core and a clad layer of an optical waveguide is provided. I'm not happy with the problem of achieving it.

[0011]

SUMMARY OF THE INVENTION Broadly speaking, the present invention comprises the deposition of an optical film by PECVD (plasma enhanced chemical vapor deposition) in the presence of a plurality of reactive gases;
And controlling the flow rate of at least one of the plurality of reactive gases to minimize unwanted absorption peaks in the deposited film.
It provides a method of depositing optical quality films by VD.

Typically, the optical film is silica. The reactive gas is usually PH ₃ , but for example, diborane: B ₂ H ₆ , arsine: AsH ₃ , titanium hydride:
TiH ₄ or germane: GeH ₄ , silicon tetrafluoride:
It can also be SiF ₄ or carbon tetrafluoride: CF ₄ .

The present invention can be used in the manufacture of silica waveguides using PECVD techniques. Total deposition pressure and SiF
Independent control of multiple reactive gases such as ₄ , N ₂ O, N ₂ and PH ₃ is performed by automatic control of the pumping rate of the vacuum pump in the six-dimensional space defined by the six elements. Be seen. In a preferred embodiment, this includes SiF ₄ flow as the first independent variable; N as the second independent variable.
₂ O flow; N ₂ flow as third independent variable; PH ₃ flow as fourth independent variable; total deposition pressure (controlled by automatic adjustment of pumping rate) as fifth independent variable; and sixth independent variable , Which includes the observed waveguide characteristics.

The inventors have found that undesired residual Si: N—H oscillators (oscillators) (observed as FTIR peaks centered at 3380 cm ⁻¹ ) after heat treatment at low temperature after deposition. While eliminating, the required refractive index difference "delta n" (delta
-N) is achieved, while keeping other variables constant, P
It was revealed that changing the H ₃ flow rate is a key factor. The present invention allows for the production of improved silica waveguides with low optical absorption in the 1.55 μm wavelength (and / or 1.30 μm wavelength) optical region, and the 1.55 μm wavelength video signal optical band (and High performance optical quality multiplexers (Mux) and demultiplexers (Dmux) with improved performance in (or) bidirectional narrow optical bands at 1.30 μm wavelength.
Can be manufactured.

The present invention is a commercially available PEC.
VD System, Novell, California, USA
"Concept On" manufactured by us Systems
e "system.

Our US copending application, filed April 13, 2001, is concerned with optimizing the optical properties of various buffers (claddings) in the space defined by five elements. , The fourth independent variable, the surprising effect of total deposition pressure is shown. The space defined by the five elements in this case consists of the following variables; the first independent variable, the SiH ₄ gas flow, typically 0.20 standard liters / minute (where “standard” refers to standard conditions). Mean flow rate by converted volume); second independent variable, N
₂ O gas stream, typically fixed at 6.00 standard liters / minute; third independent variable, N ₂ gas stream, typically 3.
Fixed at 15 standard liters / minute; fourth independent variable, total deposition pressure, which is variable; and the fifth element is
It is provided by the observed FTIR characteristics of various buffers (claddings), as reported in FIGS. 1, 3, 6, 8, 10, and 12. As reported in this application, the total deposition pressure is 2.00 Torr.
(Torr); 2.10 Torr; 2.20 Torr; 2.
30 Torr; 2.40 Torr; 2.50 Torr;
Alternatively, it can be set to 2.60 Torr.

The present invention is the fourth independent variable, P, which affects the simultaneous optimization of the optical properties of various buffers (claddings) and cores in the space defined by the six elements.
It is based on the surprising effect of H ₃ gas flow.

In accordance with the principles of the present invention, typically the first independent variable, SiH ₄ gas flow, is fixed at 0.20 standard liters / minute; the second independent variable, N ₂ O gas flow, is 6.00. The standard independent liter / minute is fixed; and the third independent variable, N ₂ gas flow, is fixed at 3.15 standard liter / minute.

The fourth independent variable, PH ₃ gas flow, is varied,
One of the following values can be taken: 0.00 standard liters / minute; 0.12 standard liters / minute; 0.25 standard liters / minute; 0.35 standard liters / minute; 0.50 standard liters / minute; Min; 0.65 standard liters / minute.

The fifth independent variable, total deposition pressure, is specifically fixed at 2.60 Torr; the sixth element is shown in FIG.
This is provided by the observed FTIR characteristics of various cores as shown in FIGS. 4, 5, 7, 9, 11 and 13.

This new technique is an undesired residual Si: N--H oscillator (3) after heat treatment at low temperature after deposition.
(Which is observed as an FTIR peak centered at 380 cm ⁻¹ ), while achieving the required “delta n”. With this technique, 1.55 μm
Enables production of improved silica waveguides with low optical absorption in the wavelength (and / or 1.30 μm wavelength) optical region, and a video signal optical band of 1.55 μm wavelength (and / or 1.30 μm wavelength) It is possible to fabricate high performance optical quality multiplexers (Mux) and demultiplexers (Dmux) with improved performance in the bidirectional narrow optical band).

The present invention also includes the following steps P
A method of depositing optical quality films by ECVD is also provided. That is, the step of creating a space defined by 6 elements, wherein 5 elements of the 6 elements correspond to 5 independent variables, respectively, and 4 independent variable groups among them are plural. For each flow of species gas, another fifth independent variable relates to total pressure and a sixth element creates the space defined by the above six elements with respect to the observed FTIR characteristics. Step and maintaining the three independent variables of the set of four independent variables and the fifth independent variable constant and to obtain the desired feature for the sixth element Depositing an optical film while varying the fourth independent variable of the other set of independent variables.

[0023]

DETAILED DESCRIPTION OF THE INVENTION Effect of PF ₃ Gas Flow on FTIR Properties of Various Cores FIG. 1 uses the PECVD technique described in our co-pending application, and
Shown are the basic FTIR spectra of various buffers (claddings) obtained after 3 hours of heat treatment in a nitrogen atmosphere at a low temperature of 800 ° C. This figure shows that the deposition pressure is from 2.00 Torr to 2.40.
When raised to Torr, the FWHM Si-O-Si "rocking mode" absorption peak (between 410 and 510 cm- ¹ ) gradually became stronger and smaller, and then the deposition pressure was increased to 2 .40
FW when raised from Torr to 2.60 Torr
HM Si-O-Si "rolling mode" absorption peak gradually weaker and larger; deposition pressure 2.00To
When raised from rr to 2.40 Torr, FWHM S
i-O-Si “In-phase expansion mode” (“in-phase”)
The e-stretching mode ") absorption peak (between 1000 and 1160 cm ^-1 ) becomes progressively stronger and smaller, which is more stoichiometric with optimal density and optimal Si-O-Si bond angle of 144 °. Showing a dynamic silica film and then setting the deposition pressure to 2.40 To
When further raised from rr to 2.60 Torr, FWHM
The Si-O-Si "in-phase stretching mode" absorption peak is gradually weaker; and the deposition pressure is 2.00 Torr.
from r to 2.40 Torr, Si-O-Si
"In-phase stretching mode" absorption peak (1080 cm ^-1 ).
And Si-O-Si "Bending vibration mode"("bendin
The separation between the (g mode ") absorption peaks (810 cm ^-1 ) becomes progressively more pronounced with a progressively deeper valley between 850 and 1000 cm ^-1 , then the deposition pressure from 2.40 Torr to 2.40 Torr. When further raised to 60 Torr, the separation gradually becomes less clear and 85
The valley between 0 and 1000 cm ^-1 becomes progressively shallower.

FIG. 2 illustrates a PECV in accordance with the principles of the present invention.
Figure 3 shows basic FTIR spectra of various cores obtained using the D technique and after 3 hours of heat treatment in a nitrogen atmosphere at a low temperature of 800 ° C. Vapor deposition pressure is 2.6
When fixed at 0 Torr, controlling PH ₃ gas flow independently of SiH ₄ gas flow, N ₂ O gas flow and N ₂ gas flow had no effect on the basic FTIR spectrum of the treated silica film. Does not reach.

The strong and small FWHM Si seen in FIG. 1 when the deposition pressure is fixed at 2.60 Torr.
-O-Si "rolling mode" absorption peak (410 and 51
0 cm ⁻¹ ) is also retained in FIG. 2 when the PH ₃ gas flow rate is gradually increased from 0.00 standard liters / minute to 0.65 standard liters / minute.

The strong and small FWHM Si seen in FIG. 1 when the deposition pressure is fixed at 2.60 Torr.
-O-Si "in-phase stretching mode" absorption peak (1000
And 1160 cm ⁻¹ ), the PH ₃ gas flow rate is 0.0
It is also retained in FIG. 2 when gradually increasing from 0 standard liters / minute to 0.65 standard liters / minute.

850 and 1000 cm ⁻¹ seen in FIG. 1 when the deposition pressure is fixed at 2.60 Torr.
Si-O-Si "in-phase stretching mode" absorption peak (1080 cm- ¹ ) and Si-O-Si with deep valley between
The separation between the “bending vibration mode” absorption peaks (810 cm ⁻¹ ) also holds in FIG. 2 when the PH ₃ gas flow rate is gradually increased from 0.00 standard liters / minute to 0.65 standard liters / minute. Has been done.

(FTI from 810 to 1000 cm ^-1
R spectrum) Figure 3 illustrates the PECVD technique described in our co-pending application, and
810 to 10 of various buffers (cladding part) obtained after heat treatment for 3 hours in a nitrogen atmosphere at a low temperature of 0 ° C.
A detailed FTIR spectrum at 00 cm ^-1 is shown. This figure shows that when the deposition pressure was increased from 2.00 Torr to 2.40 Torr,
Residual Si-OH oscillator (centered at 885 cm ^-1 )
Are gradually eliminated better, then the deposition pressure is 2.
When it was raised from 40 Torr to 2.60 Torr,
Exclusion gradually gets worse; deposition pressure is 2.00 Tor
Residual SiONH when raised from r to 2.40 Torr
And / or the SiON ₂ post-treatment compound Si-ON oscillator (centered at 950 cm ^-1 ) was gradually and better excluded, and then when the deposition pressure was further increased from 2.40 Torr to 2.60 Torr, Exclusions gradually became worse; and Si-O-Si “in-phase stretching mode” absorption peak (1080 cm ⁻¹ ) and Si when the deposition pressure was raised from 2.00 Torr to 2.40 Torr.
-O-Si "Bending vibration mode" absorption peak (810 cm
The valley between ^-1 ) becomes progressively deeper, and then the valley becomes progressively shallower when the vapor deposition pressure is further increased from 2.40 Torr to 2.60 Torr.

Referring to FIG. 4, various cores 810 to 100 obtained using the following new PECVD technique and after 3 hours heat treatment in a low temperature nitrogen atmosphere at 800 ° C.
A detailed FTIR spectrum at 0 cm ^-1 is shown.
When the deposition pressure is fixed at 2.60 Torr, the PH ₃ gas flow is controlled independently of the SiH ₄ gas flow, the N ₂ O gas flow, and the N ₂ gas flow to provide 810 to 1000 cm ⁻ of the treated silica film. ¹ has a slight positive effect on the FTIR spectrum.

The residual Si--OH oscillator (8) seen in FIG. 3 when the vapor deposition pressure was fixed at 2.60 Torr.
Exclusions (centered around 85 cm ⁻¹ ) are retained, and in fact slightly improved, when the PH ₃ gas flow rate is gradually increased from 0.00 standard liters / minute to 0.65 standard liters / minute.

Si-ON oscillators (95) of residual SiONH and / or SiON ₂ post-treatment compounds, as seen in FIG. 3 when the deposition pressure was fixed at 2.60 Torr (95
(Centered at 0 cm ⁻¹ ), the PH ₃ gas flow rate is from 0.00 standard liters / minute to 0.65 standard liters / minute
It's retained even when gradually raised to minutes, and is actually a little better.

Si—O—Si “in-phase stretching mode” absorption peak (1080 cm ⁻¹ ) and Si—O seen in FIG. 3 when the deposition pressure was fixed at 2.60 Torr.
-Si "Bending vibration mode" absorption peak (810c
The deep valley between m ⁻¹ ) is retained and indeed slightly improved when the PH ₃ gas flow rate is gradually increased from 0.00 standard liters / minute to 0.65 standard liters / minute.

(FT from 1200 to 1500 cm ^-1
IR spectra) FIG. 5 is a detailed view at 1200 to 1500 cm ⁻¹ of various cores obtained using the following new PECVD technique and after heat treatment for 3 hours in a low temperature nitrogen atmosphere at 800 ° C. The FTIR spectrum is shown. When the vapor deposition pressure is fixed at 2.60 Torr,
Controlling the PH ₃ gas flow independently of the SiH ₄ gas flow, N ₂ O gas flow and nitrogen gas flow directly affects the FTIR spectrum of the treated silica film at 1200 to 1500 cm ⁻¹ .

PH ₃ gas flow rate is 0.00 standard liter /
Minute to 0.65 standard liters / minute, the P = 0 oscillator (centered at 1330 cm ⁻¹ , 1.30 to 1.
(Which has no higher harmonics that can cause optical absorption in the 55 μm optical band) is effectively increased. This FTIR absorption peak can be used to calibrate the incorporation of phosphorus into the core.

(FT at 1500 to 1600 cm ^-1
IR spectrum) FIG. 6 illustrates the PECVD technique described in our co-pending application, and
Detailed FTIR spectra from 1500 to 1600 cm ⁻¹ of various buffers (claddings) obtained after heat treatment for 3 hours in a nitrogen atmosphere at a low temperature of 00 ° C. are shown. This figure shows 2.00 Torr to 2.60T
It shows that N = N oscillators are excluded for all deposition pressures of orr.

FIG. 7 illustrates PECVD in accordance with the principles of the present invention.
1500 of various cores obtained using the technique and after 3 hours of heat treatment in a nitrogen atmosphere at a low temperature of 800 ° C.
¹ shows a detailed FTIR spectrum at 1600 cm ⁻¹ . When the deposition pressure was fixed at 2.60 Torr, the PH ₃ gas flow was controlled independently of the SiH ₄ gas flow, N ₂ O gas flow and N ₂ gas flow, but the treated silica film 1500 to 1600 cm ^{−. It} has no effect on the FTIR spectrum at ¹ .

N for all PH ₃ gas flow rates from 0.00 standard liters / minute to 0.65 standard liters / minute.
= N oscillators are eliminated.

(FT from 1700 to 2200 cm ^-1
(IR spectrum) FIG. 8 shows various results obtained using the PECVD deposition technique described in our other pending application and after heat treatment for 3 hours in a low temperature nitrogen atmosphere at 800 ° C. 17 of the buffer (cladding part)
3 shows a detailed FTIR spectrum from 00 to 2200 cm ⁻¹ .

Si = O oscillator (centered around 1875 cm ⁻¹ , and its fourth harmonic (fourth harmonic)
ics) may cause optical absorption of 1.182 to 1.389 μm) and an unknown oscillator (centered at 2010 cm ⁻¹ , causing optical absorption in the optical band of 1.30 to 1.55 μm). It has no higher harmonics to obtain) and is not affected by any deposition pressure from 2.00 Torr to 2.60 Torr. Such a limitation is not so important since it is only the fourth harmonic of the Si = O oscillator that can cause absorption in the 1.30 to 1.55 µm optical band.

FIG. 9 illustrates PECVD in accordance with the principles of the present invention.
1700 of various cores obtained using the technique and after 3 hours of heat treatment in a nitrogen atmosphere at a low temperature of 800 ° C.
2 shows a detailed FTIR spectrum at 2200 cm ⁻¹ . When the deposition pressure was fixed at 2.60 Torr, even if the PH ₃ gas flow was controlled independently of the SiH ₄ gas flow, the N ₂ O gas flow and the N ₂ gas flow, the treated silica film 1700 to 2200 cm ^{−. It} has no effect on the FTIR spectrum at ¹ .

Si = O oscillator (centered at 1875 cm ⁻¹ and its fourth harmonic is 1.282-1.389 μ
m, which may cause optical absorption of m) and an unknown oscillator (20
Centered at 10 cm ⁻¹ and having no higher harmonics that can cause optical absorption in the optical band of 1.30 to 1.55 μm) from 0.00 standard liters / minute to 0.65 standard liters / minute It is unaffected by any PH ₃ gas flow rate per minute. This limitation is less important as only the fourth harmonic of the Si = O oscillator can cause absorption in the 1.30 to 1.55 μm optical band.

(FT at 2200 to 2400 cm ^-1
IR spectrum) FIG. 10 uses the PECVD technique described in our co-pending application, and
2200 of various buffers (cladding parts) obtained after heat treatment for 3 hours in a nitrogen atmosphere at a low temperature of 800 ° C.
2 shows a detailed FTIR spectrum from ¹ to 2400 cm ⁻¹ .

For all deposition pressures from 2.00 Torr to 2.60 Torr, the Si-H oscillator (2260c
centered around m ⁻¹ , whose third harmonic can cause optical absorption between 1.443 and 1.508 μm) is completely eliminated.

FIG. 11 illustrates a PECV in accordance with the principles of the present invention.
220 of various cores obtained using the D technique and after heat treatment for 3 hours in a low temperature nitrogen atmosphere at 800 ° C.
¹ shows a detailed FTIR spectrum from 0 to 2400 cm ⁻¹ . When the deposition pressure is fixed at 2.60 Torr, the PH ₃ gas flow is controlled independently of the SiH ₄ gas flow, the N ₂ O gas flow and the N ₂ gas flow, but the treated silica film 2200 to 2400 cm ^−. FTIR in ¹
Has no effect on the spectrum.

At all PH ₃ gas flow rates from 0.00 standard liters / minute to 0.65 standard liters / minute, the Si-H oscillator (2260 cm ^-1 is centered,
Its third harmonic, which can cause optical absorption between 1.443 and 1.508 μm), is also completely eliminated.

(FT at 3200 to 3900 cm ^-1
IR spectrum) FIG. 12 uses the PECVD technique described in our co-pending application, and
3200 of various buffers (cladding parts) obtained after heat treatment in a nitrogen atmosphere at a low temperature of 800 ° C. for 3 hours.
3 shows a detailed FTIR spectrum at 3900 cm ⁻¹ .

For all deposition pressures from 2.00 Torr to 2.60 Torr, the HO-H oscillator (3650c)
Centered around m ⁻¹ , the silica film has micropores (mi
, which shows trapped water vapor in the cro-pore), and whose second harmonic can cause optical absorption between 1.333 and 1.408 μm).

For all deposition pressures from 2.00 Torr to 2.60 Torr, the SiO-H oscillator (3510
centered around cm ⁻¹ , whose second harmonic can cause optical absorption between 1.408 and 1.441 μm) is completely eliminated.

The vapor deposition pressure is changed from 2.00 Torr to 2.60.
When raised to Torr, SiN-H oscillator (3420c
centered around m ⁻¹ , whose second harmonic can cause optical absorption between 1.445 and 1.479 μm) is gradually eliminated.

The vapor deposition pressure is changed from 2.00 Torr to 2.60.
When raising to Torr, Si: N-H oscillator (3380
centered at cm ⁻¹ , whose second harmonic can cause optical absorption between 1.445 and 1.515 μm) is gradually eliminated. This brilliant complete exclusion at low heat treatment temperatures as low as 800 ° C. is of great importance because it requires thermal cleavage of the two covalent bonds linking the nitrogen and silicon atoms of the SiO ₂ network. . Raising the deposition pressure from 2.00 Torr to 2.60 Torr resulted in such residual Si: N having two covalent bonds.
It is concluded that the formation of -H oscillators is minimized.

FIG. 13 shows 3200 to 3 of various cores obtained using the following new PECVD technique and after 3 hours of heat treatment at 800 ° C. in a low temperature nitrogen atmosphere.
A detailed FTIR spectrum at 900 cm ^-1 is shown.
When the deposition pressure was fixed at 2.60 Torr, even though the PH ₃ gas flow was controlled independently of the SiH ₄ gas flow, the N ₂ O gas flow and the N ₂ gas flow, 22
It has no effect on the FTIR spectrum from 00 to 2400 cm ⁻¹ .

The HO-H oscillator (centered at 3650 cm ^-1) at all of the PH ₃ gas flow rates from 0.00 standard liters / minute to 0.65 standard liters / minute,
It shows water vapor trapped in the micropores of a silica film, and its second harmonics are 1.333 and 1.40.
(Which can cause optical absorption between 8 μm) is also completely excluded.

At all PH ₃ gas flow rates from 0.00 standard liters / minute to 0.65 standard liters / minute, the SiO-H oscillator (centered at 3510 cm ^-1 and its second harmonic) 1.408 and 1.441μ
(which can cause optical absorption between m) is again completely eliminated.

All of the PH ₃ gas flow rates from 0.00 standard liters / minute to 0.65 standard liters / minute center the SiN-H oscillator (3420 cm ^-1 and its second harmonic 1.445 and 1.479μ
(which can cause optical absorption between m) is again completely eliminated.

The Si: N—H oscillator (centered at 3380 cm ⁻¹ and its second harmonic) was measured at all PH ₃ gas flow rates from 0.00 standard liters / minute to 0.65 standard liters / minute. The waves are 1.445 and 1.515
(which can cause optical absorption between μm) is also completely eliminated. This complete exclusion at heat treatment temperatures as low as only 800 ° C. is of great importance because it requires thermal cleavage of the two covalent bonds linking the nitrogen and silicon atoms of the SiO ₂ network. This 2.60
At a deposition pressure of Torr, increasing the PH ₃ gas flow rate from 0.00 standard liters / minute to 0.65 standard liters / minute, such residual Si with two covalent bonds:
It is concluded that the formation of N-H oscillators is also minimized.

(Potential effect of PH ₃ gas flow on optical absorption in the 1.30 to 1.55 μm optical band)
When the deposition pressure was fixed at 2.60 Torr, the PH ₃ gas flow was controlled to be 1.55 even if controlled independently of other deposition variables in the space defined by these six elements.
Various FTIR spectra show that it has no effect on the optical absorption in the μm wavelength (and / or 1.30 μm wavelength) optical region.

FIG. 2 shows that the PH ₃ gas flow is Si-O-Si "rolling mode" (460 cm ^-1 ) and Si-O-S.
It is shown that i “in-phase expansion / contraction mode” (1080 cm ⁻¹ ) does not affect both oscillators.

FIG. 4 shows a "bending vibration mode" (810 cm ^-1 ) oscillator in which the PH ₃ gas flow is Si-O-Si; Si-
OH oscillator (center: 885 cm ⁻¹ ); Si-ON oscillator (center: 950 cm ⁻¹ ); and Si—O—Si “in-phase expansion / contraction mode” oscillator (1080 cm ⁻¹ ) had a slight positive effect. To give. These 4 observed
The positive effect on the two oscillators should not affect the optical absorption of the various cores in the optical region of wavelength 1.55 μm (and / or wavelength 1.30 μm). Because the optical absorption in the 1.30 to 1.55 μm optical band is due to the very high order harmonics of these oscillators: for example, the 8th of the Si-O-Si "variable vibration mode" oscillator.
8th order harmonic; 8th order harmonic of Si-OH oscillator;
7th vibration harmonic of Si-ON oscillator; and Si-O-
This is because it is possible only by the sixth harmonic vibration of the “in-phase expansion / contraction mode” oscillator of Si.

FIG. 5 shows that the PH ₃ gas flow is 1.30 to 1.
P = O oscillator (1330 cm) without higher harmonics that can cause optical absorption in the 55 μm optical band.
^-1 ) has a very direct effect.

FIG. 7 shows that the PH ₃ gas flow does not affect the N = N oscillator (1555 cm ⁻¹ ).

FIG. 9 shows that when the PH ₃ gas flow is the Si═O oscillator (1875 cm ⁻¹ ) or the unknown oscillator (2010c).
m ⁻¹ ).

FIG. 11 shows that the PH ₃ gas flow does not affect the Si—H oscillator (2260 cm ⁻¹ ).

FIG. 13 shows that the PH ₃ gas flow is HO-H oscillator (3650 cm ^-1 ); SiO-H oscillator (3510).
cm ^-1); SiN-H oscillators ^(3420cm -1);
And that the Si: N-H oscillator (3380 cm ^-1 ) is not affected.

(Total deposition pressure and PH ₃ gas flow of 1.55μ
(Influence on mTE mode (TE mode) refractive index) FIG.
1.55 of various buffers (claddings) and cores
Transversal Electric (TE) at μm
The effect of total deposition pressure on modal index is shown. These fix the SiH ₄ gas flow at 0.20 standard liters / minute, the N ₂ O gas flow at 6.00 standard liters / minute,
A N ₂ gas flow was fixed at 3.15 standard liters / minute for vapor deposition, and then heat-treated at 800 ° C. in a nitrogen atmosphere. As described in our co-pending application, the introduction of total deposition pressure as a fourth independent variable is important for the development of optimized optical buffers (claddings) and cores, and of high quality. Obviously, the control of this parameter is of paramount importance for the reproducible completion of the optical buffer (cladding) and core. At the moment, PE
Ordinary vacuum pump systems used in CVD equipment (ie, rotary vane mechanical pumps, roots blowers (roo)
ts blower, turbo molecular pump (turbo)
-Molecular pump), or other)
It is emphasized that there are many factors that cause fluctuations in pumping speed during operation (such as fluctuations in AC power supply, fluctuations in vacuum conductance due to accumulation of residue on protective scrubber or vacuum piping system). Should be.

Thus, the PECVD deposition conditions including a fixed combination of gas flow parameters are 1.55 μm.
It was expected to suffer from the problem of poor reproducibility of TE mode refractive index in. Required "Delta n" 0.015
To achieve, FIG. 14, the optically transparent optimized buffer of refractive index 1.440 was deposited at 2.60Torr without using PH ₃ gas flow, about without using PH ₃ gas stream 2. We show that combination with a 1.455 index of refraction core deposited at 20 Torr is one possible way to achieve the required "delta n".

FIG. 15 shows various buffers (cladding portions).
And the effect of PH ₃ gas flow on the TE mode refractive index at 1.55 μm of the core. They have a SiH ₄ gas flow fixed at 0.20 standard liters / minute, an N ₂ O gas flow fixed at 6.00 standard liters / minute, and an N ₂ gas flow of 3.
Fixed at 15 standard liters / minute, vapor deposition pressure 2.60 Tor
It was fixed at r, evaporated, and then heat-treated at 800 ° C. in a nitrogen atmosphere.

In order to obtain the required "delta n" of 0.015, this FIG. 15 is 2.60 without PH ₃ gas flow.
Optically transparent optimized buffer with a refractive index of 1.440 deposited at Torr and a core with a refractive index of 1.455 deposited at 2.60 Torr using a PH ₃ gas flow of about 0.57 standard liters / minute. We show that the combination of and is another possible way to achieve the required "delta n".

(3380 cm ^{-1 of} FTIR spectrum
(Integrated area based on Si: H-H oscillator in Fig. 16)
Fixed SiH4 gas flow of 0.20 standard liters / minute, 6.
Fixed N ₂ O gas flow of 00 standard liters / minute and 3.1
Si at 3380 cm ⁻¹ in the FTIR spectra of various buffers (claddings) and cores after deposition with a fixed N ₂ gas flow of 5 standard liters / min and heat treatment in a nitrogen atmosphere at 800 ° C .: Figure 7 shows the striking effect of total deposition pressure on the N-H oscillator based integrated area.
This integrated area under the 3380 cm ⁻¹ peak of the FTIR spectrum is due to the two Si—N covalent bonds SiO ₂
This is an unmeasured relative measurement of the number of residual Si: N—H oscillators bound to the network.

The second vibration harmonics are 1.445 and 1.
Residual Si: N capable of causing optical absorption between 515 μm
It is clear that the elimination of the -H oscillator becomes progressively more complete when raising the deposition pressure from 2.00 Torr to 2.40 Torr (after low temperature heat treatment of only 800 ° C). The possible core of FIG. 16 (deposited without PH ₃ gas flow, at a pressure of about 2.20 Torr, with a refractive index of 1.
455 core), but its second vibration harmonic is 1.445.
Clearly with an excessive number of undesired residual Si: N—H oscillators that can cause optical absorption between ˜1.515 μm.

FIG. 17 shows a fixed SiH ₄ gas flow of 0.20 standard liters / minute, a fixed N of 6.00 standard liters / minute.
₂ O gas flow, deposited at a fixed N ₂ gas flow of 3.15 standard liters / min and a fixed deposition pressure of 2.60 Torr,
Then, the PH ₃ gas flow effect on the integrated area under the peak at 3380 cm ⁻¹ of the FTIR spectra of various buffer (cladding) and core Si: N—H oscillators heat-treated in a nitrogen atmosphere at 800 ° C. Show the impact. This 3
The integrated area under the FTIR peak at 380 cm ⁻¹ is almost unaffected by the PH ₃ gas flow, which is the residual Si whose second vibrational harmonics can cause optical absorption between 1.445 and 1.515 μm. : Means that the elimination of N—H oscillators is not affected by PH ₃ gas flow (after low temperature heat treatment at only 800 ° C.).

The core of FIG. 15 (PH ₃ gas flow of about 0.57
Deposited at 2.60 Torr at standard liters / minute,
A core with an index of refraction of 1.455), whose undesired residual Si: N—H oscillator, whose second harmonics can cause optical absorption between 1.445 and 1.515 μm. Clearly, there are only negligible numbers.

(PH ₃ Effect on Optical Absorption of Various Waveguides
(Influence of gas flow) FIG. 18 shows PEC obtained under the following conditions.
3 shows an infrared absorption spectrum of a VD silica waveguide. Here, the optimized buffer (cladding part) and the non-optimized core are used, and the optimized buffer (cladding part) is used.
Represents the following conditions (SiH ₄ = 0.20 standard liter / min;
N ₂ O = 6.00 standard liters / minute; N ₂ = 3.15 standard liters / minute; PH ₃ = 0.00 standard liters / minute;
After depositing the deposition pressure = 2.60Torr), then heat-treated in a nitrogen atmosphere at 800 ° C., also non-optimized core, the following conditions _(SiH 4 = 0.20 std liter / _{min; N} 2 O = 6.00 standard liters / minute; nitrogen =
3.15 standard liter / min; PH ₃ = 0.00 standard liter / min; vapor deposition pressure = 2.20 Torr), and then heat treatment is performed in a nitrogen atmosphere at 800 ° C. As expected from the FTIR spectrum discussed above, this waveguide with a "delta n" of 0.015 is associated with a large number of residual Si: H-H oscillators (and residual SiN-H oscillators), Cause an excessive optical absorption between 1.445 and 1.515 μm.

FIG. 19 shows the PECV obtained under the following conditions.
3 shows an infrared absorption spectrum of a D silica waveguide. Here, the optimized buffer (cladding part) and the optimized core are used, and the optimized buffer (cladding part) is used.
Under the following conditions (SiH ₄ = 0.20 standard liter /
Min; N ₂ O = 6.00 standard liters / min; nitrogen = 3.1
5 standard liters / minute; PH ₃ = 0.00 standard liters /
Min; deposition pressure = 2.60 Torr), and then heat-treated in a nitrogen atmosphere at 800 ° C., and the optimized core has the following conditions (SiH ₄ = 0.20 standard liter / min; N ₂ O = 6.00 standard liters / minute;
Nitrogen = 3.15 standard liters / minute; PH ₃ = 0.57 standard liters / minute; deposition pressure = 2.60 Torr), and then heat treated in a nitrogen atmosphere at 800 ° C. As expected from the FTIR spectra discussed above, this second waveguide with a "delta n" of 0.015 has a negligible number of residual Si: H-H oscillators (and residual SiN-H). Oscillator), so 1.4
It is clear that there is negligible optical absorption between 45 and 1.515 μm.

In summary, the above example relates to the simultaneous optimization of the optical properties of various buffers (claddings) and cores in the space defined by the six elements:
It shows the important role played by the fourth independent variable, PH ₃ gas flow. In a preferred embodiment, the first independent variable, the SiH ₄ gas flow is fixed at 0.20 standard liters / minute; the second independent variable, the N ₂ O gas flow is 6.00 standard liters / minute; the third independent variable, N ₂ gas flow is fixed at 3.15 standard liters / minute; fourth independent variable, PH ₃ gas flow is variable and selected from the following values: 0.00 standard liters / minute; 0.12 standard liters / minute Min; 0.25 standard liters / minute; 0.35 standard liters / minute; 0.50 standard liters / minute; 0.65 standard liters / minute.

Fifth independent variable, total deposition pressure is 2.60 To
It is fixed at rr. The sixth element is shown in FIG. 2, FIG. 4, FIG.
FIG. 14 is an observed FTIR profile of various cores as reported in FIGS. 7, 9, 11 and 13.

As already indicated, by the above technique,
Undesirable residual Si: N- after low temperature heat treatment after deposition
It is possible to eliminate the H oscillator (observed as an FTIR peak centered at 3380 cm ⁻¹ ) while achieving the required “delta n”, resulting in:
An improved silica waveguide is provided that has low optical absorption in the 1.55 μm wavelength (and / or 1.30 μm wavelength) optical region, and a 1.55 μm wavelength video signal optical band (and / or 1. It becomes possible to manufacture high performance optical quality multiplexers (Mux) and demultiplexers (Dmux) with improved performance in the 30 μm wavelength bidirectional narrow optical band).

Comparing the various PECVD techniques summarized in Table 1 with our co-pending application, the PECVD technique proposed to obtain the buffer (cladding) is:
N ₂ , O ₂ , HNO, NH ₃ , from the micropores of growing silica films to their surface and through their gaseous boundary layers, which are present near their surface, N ₂ , O ₂ , HNO, NH ₃ , Due to the improved elimination of gaseous compounds of H ₂ O and H ₂ , undesirable S
In order to improve the elimination of _i-O x _-H y -N _z compounds,
Unique in using the total deposition pressure and independent control of SiH ₄ , N ₂ O and N ₂ gases through automatic control of the pumping speed of the vacuum pump in the space defined by the five elements. I know there is. This effect is due to the fact that the equilibrium is affected by changing the number of gaseous compounds. That is, the number of molecules of the gaseous compound is different from 3 which is the number of molecules of the gaseous reaction compound (SiH ₄ (g) + 2N ₂ O (g) → various products).

The following items are used in the various references cited in the above table: SiH ₄ / N ₂ O gas flow ratio in the space defined by two factors (unique independent variable, SiH ₄ / N ₂ O ratio and observed variables, observed characteristics); SiH ₄ / N ₂ O / N ₂ gas flow ratio in the space defined by the three elements (first independent variable, SiH ₄ / N) ₂ O ratio, second independent variable, N ₂ O /
Nitrogen ratio and observed variables, observed characteristics); SiH ₄ , N ₂ in the space defined by the four elements
O, N ₂ gas flow (first independent variable, SiH ₄ flow, second independent variable, N ₂ O flow, third independent variable, nitrogen flow and observed variables, observed properties).

In accordance with the principles of the present invention, a striking effect of a fourth independent variable, PH ₃ gas flow, on the simultaneous optimization of various optical properties was deposited in the space defined by the six elements. This is clearly shown by the FTIR spectra of various cores.

In one specific example, the first independent variable, S
iH ₄ gas flow was fixed at 0.20 standard liters / minute;
The second independent variable, N ₂ O gas flow, was fixed at 6.00 standard liters / minute; the third independent variable, N ₂ gas flow was 3.1.
5 is fixed to standard liters / min; fourth independent variable, PH ₃
The gas flow is 0.00 standard liter / minute, 0.12 standard liter / minute, 0.25 standard liter / minute, 0.35 standard liter / minute, 0.50 standard liter / minute, and 0.6 standard liter / minute.
Variable from 5 standard liters / minute; Fifth independent variable,
The total deposition pressure is fixed at 2.60 Torr; and the sixth element, which forms a part of the space defined by the six elements, is shown in FIG. 2, FIG. 4, FIG. 5, FIG. 7, FIG. as well as,
FIG. 14 is an observed FTIR characteristic of various cores as reported in FIG. 13, which shows a pressure of 2.60 Torr.
When fixed at 1.55 μm wavelength (and / or 1.30 μm), the PH ₃ gas flow is controlled independently of other deposition variables in the space defined by these six elements.
It shows that it has no effect on the optical absorption in the (wavelength) optical region.

In order to achieve the required 0.015 “delta n” (TE mode, 1.55 μm) between the waveguide buffer (cladding) and the core, the first waveguide option is refraction Clear optimized buffer with a rate of 1.440 (SiH ₄ gas stream fixed at 0.20 standard liters / minute, N ₂ O gas stream fixed at 6.00 standard liters / minute, N ₂ gas The flow was fixed at 3.15 standard liters / minute, the PH ₃ gas flow was fixed at 0.00 standard liters / minute and the pressure was fixed at 2.60 Torr for vapor deposition, then in a nitrogen atmosphere at 800 ° C. Heat treated) and S
iH ₄ gas flow was fixed at 0.20 standard liters / minute, N 2
_{The 2} O gas stream was fixed at 6.00 standard liters / minute, the nitrogen gas stream was fixed at 3.15 standard liters / minute, the PH ₃ gas stream was fixed at 0.00 standard liters / minute, and the pressure was set to 2 ．
It is shown in FIG. 14 that a core with an index of refraction of 1.455, fixed and vapor deposited at 20 Torr, and then heat treated in a nitrogen atmosphere at 800 ° C. is shown.

Unfortunately, FIG. 16 shows that this first core option is important for a Si: N—H oscillator with _two Si—N covalent bonds to the SiO ₂ network.
It is shown to have an integrated area under the FTIR peak at 380 cm ⁻¹ , and the second harmonics of these Si: N—H oscillators show optical absorption between 1.445 and 1.515 μm. It is predicted from FIG. 16 that the optical properties of the waveguide resulting from this first core option may not be satisfactory, as this may occur. From FIG. 18, this first core option is due to the excess residual Si: H—H oscillator number (and residual SiN—H oscillator number) that causes excess optical absorption between 1.445 and 1.515 μm. It is confirmed to be accompanied by excessive infrared absorption.

An alternative option to achieve the required "delta n" of 0.015 between the waveguide buffer (cladding) and core is shown in FIG. In this figure, an optically clear optimized buffer with a refractive index of 1.440 (SiH ₄ gas flow fixed at 0.20 standard liters / minute and N ₂ O gas stream at 6.00 standard liters). / Min, the N ₂ gas flow was fixed at 3.15 standard liters / minute, the PH ₃ gas flow was fixed at 0.00 standard liters / minute, and the pressure was fixed at 2.60 Torr for vapor deposition. Then, heat treated in a nitrogen atmosphere at 800 ° C.), S
iH ₄ gas flow was fixed at 0.20 standard liters / minute, N 2
_{The 2} O gas flow was fixed at 6.00 standard liters / minute and N ₂
The gas flow was fixed at 3.15 standard liters / minute, the PH ₃ gas flow was fixed at 0.57 standard liters / minute, and the pressure was 2.
It has been shown that an optimized core with an index of refraction of 1.455 heat-deposited at 60 Torr fixed and then heat-treated in a nitrogen atmosphere at 800 ° C. is also possible. In this case, the secondary vibration harmonics are 1.445 and 1.51.
A reduced integrated area under the FTIR peak at 3380 cm ⁻¹ of the residual Si: N—H oscillator causing optical absorption between 5 μm is accompanied by this optimized core option, and this integrated area is ₃ gas streams (only 8
It is shown in FIG. 17 that it is hardly affected (after heat treatment at a low temperature of 00 ° C.). Therefore, it is predicted from FIG. 17 that the optical properties of the waveguide obtained from this optimized core option will be excellent. This optimized core option has a negligible number of residual Si: H-H oscillators (and residual SiN-H oscillators).
It is confirmed from FIG. 19 that there is an excellent optical transparency depending on the number of.

This new technique provides an improved silica waveguide with low optical absorption in the 1.55 μm wavelength (and / or 1.30 μm wavelength) optical region, and a 1.55 μm wavelength video signal optical band (and (Or) low temperature after deposition to enable the production of high performance optical quality multiplexers (Mux) and demultiplexers (Dmux) with improved performance in the 1.30 μm wavelength bidirectional narrow optical band. It is possible to achieve the required “delta n” while eliminating unwanted residual Si: N—H oscillators after heat treatment.

Many modifications of the invention are possible as will be appreciated by those skilled in the art. From the viewpoint of not limiting the examples, temperatures different from 400 ° C., especially 100 to 650.
PECVD silica films can be deposited at any temperature between 0 ° C.

The PECVD equipment is Novellus Co
It may be different from the ncept One. The basic requirements are four basic control parameters: S
It is to provide independent control of iH ₄ gas flow rate, N ₂ O gas flow rate, N ₂ gas flow rate and total deposition pressure.

Local optimum values of buffer (cladding part) in the space for these four independent variables (0.20 standard liter / min SiH ₄ gas flow, 6.00 standard liter / min N ₂ O gas flow, 3 .15 standard liters / min _{N 2} gas flow and total deposition pressure of 2.60Torr) is the same Novel
lus Concept set of different numerical values using One device may also have _{(SiH 4,} N 2 O, a set of _{N 2} and deposition pressure).

The local optimum value of the buffer (cladding part) is
Different sets of numbers (Si
H ₄ , N ₂ O, N ₂ and vapor deposition pressure). The local optimum of the core in space (0.20 standard liters / min SiH ₄ gas flow, related to these five independent variables,
6.00 standard liters / minute N ₂ O gas stream, 3.15 standard liters / minute N ₂ gas stream, 0.57 standard liters / minute
Min PH ₃ gas flow and total deposition pressure of 2.60 Torr)
, But using the same Novellus Concept One device, different sets of numbers (SiH ₄ , N ₂ O, N ₂ ,
PH ₃ and vapor deposition pressure). It is also possible that the local optimum of this core has a different set of numbers (set of SiH ₄ , N ₂ O, N ₂ , PH ₃ and deposition pressure) in other PECVD equipment.

[Delta n] is different from 0.015, and 0.
It can range between 005 and 0.020. Silicon source gas: SiH ₄ , SiCl ₄ , SiF ₄ ,
Si ₂ H ₆ , SiH ₂ Cl ₂ , SiCl ₂ F ₂ , SiH
₂ F ₂ or H, Cl, F, Br or I can be replaced with an alternative silicon containing gas such as any other silicon containing gas used.

Oxidation gas
s) N ₂ O is replaced with O ₂ , NO ₂ , H ₂ O, H
It can be replaced by alternative oxygen-containing gases such as ₂ O ₂ , CO, CO ₂ .

The carrier gas N ₂ is replaced with He, Ne,
It can be replaced by an alternative carrier gas such as Ar or Kr.

Doping gas
s) PH ₃ is replaced with B ₂ H ₆ , AsH ₃ , TiH ₄ ,
It can be replaced with an alternative doping gas such as GeH ₄ , SiF ₄ or CF ₄ .

The high temperature heat treatment in nitrogen can be carried out at a temperature different from 800.degree. A preferred range is 400 to 1200 ° C.

The optical region in question is 1.30 to 1.55
It is not limited to the μm optical region. because,
This is because the larger vibrational harmonics of the rejected oscillator have other optical benefits at longer or shorter wavelengths. The first, second, third and fourth harmonics of these oscillators are also covered by this patent.

Applications of the present invention include photonics devices other than Mux / Dmux devices; semiconductor devices; Micro El
electro Mechanical Systems
(MEMS); Biochip; Lab-on-a-ch
ip devices; and various other manufacturing processes involving high quality silica films such as multi-chip modules.

While the present invention has been described and illustrated in detail, these are by way of illustration only and are not to be considered limiting, the nature and scope of the invention being limited only by the terms of the appended claims. You should clearly understand what is done.

[Brief description of drawings]

The invention will be described in more detail by way of example only with reference to the accompanying drawings.

FIG. 1 shows basic FTIR spectra of various buffers (claddings). These were obtained by the PECVD technique described in our pending patent application, followed by a heat treatment for 3 hours at a low temperature of 800 ° C. under a nitrogen atmosphere.

FIG. 2 shows basic FTIR spectra of various cores. These are the new Ps at 2.60 Torr
It is obtained by the ECVD technique and the subsequent heat treatment for 3 hours at a low temperature of 800 ° C. in a nitrogen atmosphere.

FIG. 3 shows various buffers (cladding part) 81.
3 shows a detailed FTIR spectrum from 0 to 1000 cm ⁻¹ . These were obtained by the PECVD technique described in our other pending patent applications, followed by a heat treatment for 3 hours at a low temperature of 800 ° C. under a nitrogen atmosphere.

FIG. 4 shows 810 to 1000 cm of various cores.
¹ shows a detailed FTIR spectrum at ^-1 . These were obtained by the new PECVD technology at 2.60 Torr and the subsequent heat treatment at 800 ° C. for 3 hours in a nitrogen atmosphere.

FIG. 5 shows various cores 1260 to 1500c.
3 shows a detailed FTIR spectrum at m ⁻¹ . These are the new PECVD technology at 2.60 Torr,
It was obtained by subsequent heat treatment at a low temperature of 800 ° C. for 3 hours in a nitrogen atmosphere.

FIG. 6 shows various buffers (cladding portions) of 15
¹ shows a detailed FTIR spectrum from 00 to 1600 cm ⁻¹ . These are the PECVD technique described in our co-pending application, followed by a nitrogen atmosphere.
It was obtained by heat treatment at a low temperature of 00 ° C. for 3 hours.

FIG. 7 shows various cores 1500-1600c.
3 shows a detailed FTIR spectrum at m ⁻¹ . These are the new PECVD technology at 2.60 Torr,
It was obtained by subsequent heat treatment at a low temperature of 800 ° C. for 3 hours in a nitrogen atmosphere.

FIG. 8 shows 17 of various buffers (cladding part).
3 shows a detailed FTIR spectrum from 00 to 2200 cm ⁻¹ . These were obtained by the PECVD technique described in our other pending patent applications, followed by a heat treatment for 3 hours at a low temperature of 800 ° C. under a nitrogen atmosphere.

FIG. 9 shows various cores 1700-2200c.
3 shows a detailed FTIR spectrum at m ⁻¹ . These are the new PECVD technology at 2.60 Torr,
It was obtained by subsequent heat treatment at a low temperature of 800 ° C. for 3 hours in a nitrogen atmosphere.

FIG. 10 is a detailed FTIR for various buffers (claddings) from 2200 to 2400 cm ⁻¹ .
The spectrum is shown. These were obtained by the PECVD technique described in our other pending patent applications, followed by a heat treatment for 3 hours at a low temperature of 800 ° C. under a nitrogen atmosphere.

FIG. 11 shows various cores 2200-240.
A detailed FTIR spectrum at 0 cm ^-1 is shown.
These were obtained by the new PECVD technology at 2.60 Torr and the subsequent heat treatment at 800 ° C. for 3 hours in a nitrogen atmosphere.

FIG. 12 is a detailed FTIR from 3200 to 3900 cm ⁻¹ for various buffers (claddings).
The spectrum is shown. These were obtained by the PECVD technique described in our other pending patent application, followed by a low temperature of 800 ° C. for 3 hours under a nitrogen atmosphere.

FIG. 13 shows various cores 3200-390.
A detailed FTIR spectrum at 0 cm ^-1 is shown.
These were obtained by the new PECVD technology at 2.60 Torr and the subsequent heat treatment at 800 ° C. for 3 hours in a nitrogen atmosphere.

FIG. 14 shows the effect of total deposition pressure on the TE mode at 1.55 μm for various buffers (claddings) and cores. These have a SiH ₄ gas flow of 0.2
Fixed at 0 standard liters / minute, N ₂ O gas flow fixed at 6.00 standard liters / minute, N ₂ gas flow fixed at 3.15 standard liters / minute for vapor deposition, and then under nitrogen atmosphere 800
It was heat treated at ° C.

FIG. 15 shows the PH for TE mode at 1.55 μm for various buffers (claddings) and cores.
₃ shows the influence of the gas flow rate. They fixed the SiH ₄ gas flow to 0.20 standard liters / min and the N ₂ O gas flow to 6.
It was fixed at 00 standard liters / minute, the N ₂ gas flow was fixed at 3.15 standard liters / minute, the vapor deposition pressure was fixed at 2.60 Torr for vapor deposition, and then heat-treated at 800 ° C. in a nitrogen atmosphere.

FIG. 16 shows the effect of total deposition pressure on the integrated area of the FTIR peak at 3380 cm ⁻¹ of a Si: N—H oscillator for various buffers (claddings) and cores. These were a SiH ₄ gas flow fixed at 0.20 standard liters / minute, an N ₂ O gas flow fixed at 6.00 standard liters / minute, and an N ₂ gas flow fixed at 3.15 standard liters / minute. It was vapor-deposited and then heat-treated at 800 ° C. in a nitrogen atmosphere.

FIG. 17 shows the effect of PH ₃ gas flow rate on the integrated area of the FTIR peak at 3380 cm ⁻¹ of Si: N—H oscillator for various buffers (claddings) and cores. These have a SiH ₄ gas flow of 0.20
Fixed at standard liter / min, N ₂ O gas flow fixed at 6.00 standard liter / min, N ₂ gas flow fixed at 3.15 standard liter / min, vapor deposition pressure fixed at 2.60 Torr for vapor deposition Then, it was heat-treated at 800 ° C. in a nitrogen atmosphere.

FIG. 18 is a PECVD obtained using:
The infrared absorption spectrum of a silica waveguide is shown. They are,
Optimization buffer (cladding part) (SiH ₄ = 0.20 standard liter / minute; N ₂ O = 6.00 standard liter / minute;
N ₂ = 3.15 standard liters / minute; PH ₃ = 0.00 standard liters / minute; vapor deposition pressure = 2.60 Torr), and
Non-optimized core (SiH ₄ = 0.20 standard liter / min;
N ₂ O = 6.00 standard liters / minute; N ₂ = 3.15 standard liters / minute; PH ₃ = 0.00 standard liters / minute;
Vapor deposition pressure = 2.20 Torr) in a nitrogen atmosphere at 800 ° C
It was heat treated in.

FIG. 19 is a PECVD obtained using:
The infrared absorption spectrum of a silica waveguide is shown. They are,
Optimization buffer (cladding part) (SiH ₄ = 0.20 standard liter / minute; N ₂ O = 6.00 standard liter / minute;
N ₂ = 3.15 standard liters / minute; PH ₃ = 0.00 standard liters / minute; vapor deposition pressure = 2.60 Torr), and
Optimization Core _(SiH 4 = 0.20 std liter / min; N
₂ O = 6.00 standard liters / minute; N ₂ = 3.15 standard liters / minute; PH ₃ = 0.57 standard liters / minute; vapor deposition pressure = 2.60 Torr) was heat-treated at 800 ° C. under a nitrogen atmosphere. It is a thing.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Jonathan Lachance             Quebec, Granby, Bru, Canada             Flannel 535 (72) Inventor Manuel Grondin             Quebec, Canada, Granby, Aussie             492 (72) Inventor Stefan Bren             Quebec, Sherbrooke, TE             Troll 1400 F term (reference) 2H047 PA05 QA04 TA23 TA44                 4G014 AH14 AH21                 4G059 AA11 AB09 AB11 AB14 AC09                       EA05 EB02                 4K030 AA06 AA13 AA14 AA18 AA20                       BA26 BA29 BA44 DA09 FA10                       FA14 JA05 JA09 JA10

Claims (29)

[Claims] 1. A method for depositing an optical quality film by PECVD (plasma enhanced CVD), comprising: a step of depositing an optical film by PECVD in the presence of plural kinds of gases; and an unnecessary absorption peak in the deposited film. Controlling the flow rate of at least one of the plurality of gases in order to minimize it. The method of depositing an optical quality film by PECVD as described above. 2. The method of claim 1, wherein the optical film is silica. 3. The method of claim 1, wherein the flow rate of gases other than the at least one gas of the plurality of gases is maintained substantially constant. 4. The total deposition pressure is maintained substantially constant.
The method according to claim 3. Wherein said plural kinds of gas comprises PH _3, wherein the flow rate of the PH ₃ is varied in order to minimize unwanted absorption peak in the deposited layer, The method of claim 1. 6. The method of claim 5, wherein gases other than the at least one gas of the plurality of gases include SiH ₄ , N ₂ O and N ₂ . 7. The method of claim 6, wherein the total pressure is also maintained substantially constant during deposition. 8. The at least one gas is B
_The gas selected from the group consisting of ₂ H ₆ , AsH ₃ , TiH ₄ , GeH ₄ , SiF ₄ and CF _4.
The method described. 9. The method of claim 1, wherein the plurality of gases includes at least three gases whose flow rates are maintained substantially constant and a fourth gas whose flow rates are varied. . 10. The three types of gases are SiH ₄ and N ₂
O, made _{N 2,} the fourth gas is PH _3, The method of claim 9. 11. The SiH ₄ gas flow rate is fixed at about 0.20 standard liters / minute, and the N ₂ O gas flow rate is about 6.0.
It is fixed at 0 standard liter / min and the gas flow rate of N ₂ is 3.
Fixed at 15 standard liters / minute, and the gas flow rate of PH ₃ is 0.00 standard liters / minute, 0.12 standard liters / minute, 0.25 standard liters / minute, 0.35 standard liters / minute, 0.50 standard liters / minute and 0.65
2. A variable in standard liters / minute values.
The method described in 0. 12. The method of claim 11, wherein the total deposition pressure is fixed at about 2.60 Torr. 13. The method of claim 1, further comprising subjecting the film to a post-deposition heat treatment. 14. The heat treatment after vapor deposition is 400 to 12
The method according to claim 13, which is carried out at a temperature between 00 ° C. 15. The method of claim 14, wherein the post-deposition heat treatment is performed at about 800 ° C. 16. The method according to claim 15, wherein the post-deposition heat treatment is performed in the presence of nitrogen. 17. The method of claim 2, wherein the film is deposited at a temperature between 100 and 650 ° C. 18. The method of claim 17, wherein the film is deposited at about 400 ° C. 19. The method of claim 1, wherein the optical film forms part of an optical waveguide. 20. A method of vapor deposition of an optical quality film by PECVD (plasma enhanced CVD), the method comprising: creating a space defined by six elements, wherein five elements of the six elements are included. Is 5
One set of four independent variables, of which four sets of independent variables relate to the flow rates of each of the gases, the fifth independent variable relates to the total pressure, and the sixth factor is the observation. Creating a space defined by the above six elements for the feature of the FTIR performed, keeping three independent variables of the set of four independent variables and the fifth independent variable constant, and The step of: depositing an optical film while varying another fourth independent variable of the set of four independent variables to obtain a desired characteristic for the sixth element. Optical quality film deposition method. 21. The method of claim 20, wherein the optical film is a silica film. 22. The plurality of kinds of gases include a source gas, an oxidizing gas, a carrier gas, and a doping gas, and each of the four independent variable sets includes the source gas,
22. The method of claim 21, relating to the flow rates of oxidizing gas, carrier gas, and doping gas. 23. The source gas is SiH ₄ , SiCl ₄ .
₄ , SiF ₄ , Si ₂ H ₆ , SiH ₂ Cl ₂ , SiCl
_{2 F 2, SiH 2 F 2} , and, H, Cl, F, Br or I is selected from the group consisting of some other silicon-containing gas used, the method according to claim 22. 24. The oxidizing gas is N ₂ O, O ₂ , N
_{O 2, H 2 O, H} 2 O 2, CO, and is selected from the group consisting of CO _2, The method of claim 23. 25. The carrier gas is N ₂ , He or N.
3. A compound selected from the group consisting of e, Ar and Kr.
The method according to 4. 26. The doping gas is PH ₃ , B
₂ H ₆ , AsH ₃ , TiH ₄ , GeH ₄ , SiF ₄ , C
It is selected from the group consisting of F _4, The method of claim 25. 27. The method of claim 20, further comprising performing a post-deposition heat treatment at a temperature between 400 and 1200 ° C. 28. The method of claim 27, wherein the post-deposition heat treatment is performed in the presence of nitrogen. 29. The method of claim 27, wherein the post-deposition heat treatment is performed at about 800 ° C.